Answer
At the heart of our Milky Way galaxy lies a supermassive black hole (SMBH). Andrea Ghez's groundbreaking work using high-resolution imaging techniques revealed the presence of this SMBH, named Sagittarius A* (Sgr A*). By tracking the orbits of stars near the Galactic Center, she provided robust evidence for the existence of this extraordinarily massive and fascinating celestial object that governs the dynamics of our galaxy.